In recent years, development of a CO2 cycle power generation system in which carbon dioxide, fuel, and oxygen are introduced into a combustor, and power generation is performed by rotating a turbine by generated combustion gas has been advanced. According to the CO2 cycle power generation system, it is possible to simultaneously perform the power generation and CO2 recovery, and to perform high-efficiency power generation. Hereinafter, the turbine used for the CO2 cycle power generation system is denoted as a CO2 turbine.
In the CO2 turbine, a temperature of the combustion gas being a working fluid is high, and a pressure difference between inside and outside of a casing is large. Therefore, it is impossible to sufficiently seal between adjacent members constituting the casing according to a conventional sealing structure. For example, in case of a steam turbine, the pressure difference between inside and outside of the casing is large such as approximately 30 MPa, but a temperature of the working fluid is low such as approximately 600° C. On the other hand, in case of a gas turbine, the temperature of the working fluid is high such as 1000° C. or more, but the pressure difference between inside and outside of the casing is low such as approximately 3 MPa. In case of the CO2 turbine, the pressure difference between inside and outside of the casing is large such as approximately 30 MPa, and the temperature of the working fluid is high such as 1000° C. or more.
FIG. 10 is a sectional view illustrating an example of the CO2 turbine in a vicinity of a final stage. A CO2 turbine 100 includes a stationary component 111 and a rotary component 112. The stationary component 111 includes an inner casing 113 in a cylindrical shape and a not-illustrated outer casing.
A stationary blade cascade including a plurality of stationary blades 114 in a circumferential direction is disposed inside the casing 113. The stationary blade 114 includes an inside shroud 115, a stationary blade body 116, and an outside shroud 117 in this order from an inner side. An extension part 118 to prevent a heat input from the combustion gas to the casing 113 is further disposed at the stationary blade 114. Besides, a rotor blade cascade including a plurality of rotor blades 123 implanted to a rotor wheel 122 of a turbine rotor 121 at a constant interval in a circumferential direction is disposed at a direct downstream side of the stationary blade cascade. The stationary blade cascade and the rotor blade cascade are alternately provided along an axial direction. One turbine stage is made up of the stationary blade cascade and the rotor blade cascade at the direct downstream side of the stationary blade cascade. Note that in the drawing, a reference numeral 124 indicates a flow of the combustion gas. Besides, in the drawing, a reference numeral 125 indicates a flow of a cooling medium.
The casing 113 includes a first cylinder part 126 and a second cylinder part 127, for example, from an upstream side toward a downstream side of the flow of the combustion gas. Though it is not illustrated, the first cylinder part 126 is fixed at a part other than an end part at the second cylinder part 127 side. Besides, the second cylinder part 127 is fixed at a part other than an end part at the first cylinder part 126 side. A gap between the first cylinder part 126 and the second cylinder part 127 is sealed by a sealing part 128. An inner surface of the first cylinder part 126 is covered by the extension part 118, and the first cylinder part 126 is cooled by the cooling medium flowing between the first cylinder part 126 and the extension part 118.
The sealing part 128 includes, for example, a sealing member having a connection fin. As for the sealing member, a part except the connection fin is housed in an inside part of the second cylinder part 127, and the connection fin is in contact with an outer surface of the first cylinder part 126.
In case of the CO2 turbine 100 having the above-stated structure, the cooling medium is in contact with the inner surface of the first cylinder part 126 and a temperature thereof becomes low. On the other hand, the combustion gas is in contact with an inner surface of the second cylinder part 127 and a temperature thereof becomes high.
When the temperature of the second cylinder part 127 becomes higher than the temperature of the first cylinder part 126, an elongation (thermal elongation) in a radial direction resulting from a thermal expansion of the second cylinder part 127 becomes large compared to a thermal elongation in the radial direction of the first cylinder part 126. A positional displacement in the radial direction occurs between the first cylinder part 126 and the second cylinder part 127 resulting from a difference in thermal elongations in the radial direction. Besides, as for the axial direction, a positional displacement in the axial direction occurs resulting from the thermal elongations in each direction of the first cylinder part 126 and the second cylinder part 127. In case of the illustrated sealing part 128, it is possible to follow the positional displacement in the axial direction, but it is impossible to enough follow the positional displacement in the radial direction.
Besides, one illustrated in FIG. 11 can be cited as the sealing part 128. The sealing part 128 illustrated in FIG. 11 includes a pair of groove parts disposed at inner surfaces of the first cylinder part 126 and the second cylinder part 127, and an annular sealing member housed in the pair of groove parts. The sealing part 128 as stated above is sealed by pressing the sealing member to side surfaces of the groove parts caused by a pressure difference between inside and outside of the casing 113. However, in case of the sealing part 128 as stated above, it is possible to follow the positional displacement in the radial direction, but it is impossible to enough follow the positional displacement in the axial direction.
Further, one illustrated in FIG. 12 can be cited as the sealing part 128. The sealing part 128 illustrated in FIG. 12 includes a thin plate state sealing member extending over an end face of the first cylinder part 126 and an end face of the second cylinder part 127. The sealing part 128 as stated above is able to follow positional displacements in the radial direction and the axial direction between the first cylinder part 126 and the second cylinder part 127 owing to an elastic deformation of the sealing member. However, when the pressure difference between inside and outside of the casing 113 becomes large, there is a possibility in which the sealing member is broken caused by shortage of strength. On the other hand, when the strength of the sealing member is increased, the elastic deformation is difficult to occur, and it is impossible to enough follow the positional displacements in the radial direction and the axial direction.
As stated above, when a gap between a pair of cylinder parts whose temperatures are different is sealed, it is necessary to follow positional displacements in both a radial direction and an axial direction.
An object of the present invention is to provide a sealing structure capable of sealing between a pair of cylinders whose temperatures are different.